Wheel brake assembly

ABSTRACT

A wheel brake assembly in which the webs of brake shoes are held in a planar alignment between and supported by a pair of parallel-spaced interconnected supporting plates, in turn supported by an axle or spindle. A pair of brake contracting springs interconnect the brake shoes, and these springs are positioned with one spring being against the outer surface of each plate. An inner edge of each of the plates is circular and independently adapted to attach to an axle housing, whereby the brake assembly may be readily welded to an axle housing.

This application is a continuation of application Ser. No. 796,346,filed May 12, 1977, and now U.S. Pat. No. 4,150,736, which is acontinuation of application Ser. No. 638,594, filed Dec. 8, 1975, nowabandoned, which is a continuation of application Ser. No. 444,736,filed Feb. 22, 1974, now abandoned, which was an application for thereissue of U.S. Pat. No. 3,788,432.

BACKGROUND OF THE INVENTION

Towed vehicles weighing more than certain state regulated weights arerequired to have brakes which may be operated from the cab of the towingvehicle. In general, such vehicles as mobile homes, recreationaltrailers, and certain other towed vehicles such as boat trailers employelectrically-operated brakes and such type brakes have been in use for anumber of years. Typical illustrations of such brakes are contained inU.S. Pat. Nos. 3,134,463 and 3,244,259.

Recently there has been a movement reflected by S.A.E. and Governmentregulations to require a greater usage of brakes on towed vehicles,extending the requirement to vehicles of lower weight than previouslyrequired and requiring in some instances that all wheels of the towedvehicles be equipped with brakes. The latter requirement is in contrastto past practices in which, for example, mobile homes having a total ofsix or eight wheels would have brakes on only two or four of them. Theresult is that there has currently appeared a substantially increasingneed for electrically equipped brake assemblies. This, of course, is inturn bringing about significantly increased costs of such vehicles,particularly since existing type electrical brakes have a good manycomponents and are fairly expensive to manufacture.

In addition to the substantial costs of existing type electrical brakes,it has been found that in many instances their operation has been lessthan satisfactory. For example, it has been found that balanced loadingof brake lining against brake drums is not often achieved, resulting ina deterioration in available braking force. This problem exists withmechanical, hydraulic, and air-operated drum brakes as well and,accordingly, the present invention is directed to drum-type brakes ingeneral.

Another common problem has been that excessive forces are concentratedon certain components of the operating mechanisms causing deformation orfailure of components, resulting in complete or nearly complete brakefailure.

SUMMARY OF THE INVENTION

Accordingly, the object of the present invention is to provide a new andimproved brake assembly which is less expensive to manufacture thanprevious brake assemblies and yet is of more reliable construction andwill provide greater assurance of uniform braking action over the fullanticipated life of the brake assembly.

In accordance with the invention, a wheel brake assembly is constructedfor drum-type brakes in which the webs of brake shoes are supportedbetween a pair of parallel spaced interconnected supporting plates,supporting surfaces for parallel planes, in turn supported by an axle orspindle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of an electrical brake assembly ascontemplated by the invention.

FIG. 1A is an exploded view of an alternate form of an electromagnet andmounting brackets.

FIG. 1B is a sectional view of an assembled electromagnet of the typeshown in FIG. 1A.

FIG. 1C is a pictorial view of a splash plate usable with the electricalbrake assembly shown in FIG. 1.

FIG. 2 is an elevational view of an assembled electrical brake.

FIG. 3 is a sectional view along lines 3--3 of FIG. 2.

FIG. 4 is a pictorial view illustrative of a liquid or air-operatedversion of the present invention.

FIG. 5 is a sectional view along lines 5--5 of FIG. 4 and wherein thebraking assembly is pneumatically operated.

FIG. 6 is a pictorial view of a version of the invention wherein adouble-acting hydraulic cylinder operates braking shoes through a pairof lever arms.

FIG. 7 is a pictorial view of a hydraulic version of the presentinvention wherein two single-acting hydraulic cylinders provide a forceon front and back brake-shoes, respectively.

FIG. 8 is a pictorial view of a hydraulic brake version of the presentinvention wherein a single acting hydraulic cylinder provides anoperating force.

FIG. 9 is an exploded pictorial view of a brake assembly similar to thatillustrated in FIG. 4 except that there is additionally provided meansfor mechanically operating the brake assembly.

FIG. 10 is an exploded pictorial view of an embodiment of the inventionwherein braking force is applied solely by mechanical means.

FIG. 11 is a sectional view along lines 11--11 of FIG. 10.

FIG. 12 is an exploded pictorial view of an alternate form of mechanicalbrake.

FIG. 13 is an exploded view of an alternate assembly, to that shown inFIG. 9, for adding a mechanical braking mechanism to a hydraulic brake.

DETAILED DESCRIPTION OF THE INVENTION

The non-rotating components of brake assembly 10 are shown opposite theparenthesis designated by the numeral 16 in FIG. 1. Triangular-shapedplates 18 and 20, referred to herein as "backing plates", are coupledtogether in a spaced relationship by spacer rivets 22, 24 and 26, havingend regions 28 adapted to accept and extend through aligned apertures30, 32 and 34, spaced inward of truncated corners of plates 18 and 20.Plates 18 and 20 are further connected by anchor pin 36, of largerdiameter than spacer rivets 22, 24 and 26, having end regions 38 adaptedto fit and extend through aligned bores 40, centrally formed near upperedge 42 of each of plates 18 and 20. Actuating lever arm 44 is pivotablysupported by aperture 46 on upper rivet 24 between backing plates 18 and20. It is of a thickness between 0.180 and 0.190 inches, is essentiallyeliptical in form and is provided with an intermediate elongated opening48 which facilitates freedom of movement about spindle 50 to whichplates 18 and 20 are to be welded. Aperture 46 is centrally positionednear upper end 52 of lever arm 44, being dimensioned to accept theenlarged diameter portion 54 of rivet 24. Rectangular shaped expansionlug 56 is disposed vertically above pivotal aperture 46 of lever arm 44and is adapted to actuate brake shoes 58 and 60 in a manner to befurther described.

A pair of inwardly disposed spaced fingers 62 are integrally formednormal to lower portion of lever arm 44 and are adapted to freely acceptmating aperture 64 provided in electromagnet 66. Electromagnet 66 isurged into spring biased engagement with armature plate or disc 67 ofhub and drum assembly 12, in a manner to be further described, bycompression spring 69 retained about fingers 62, by retaining plug 63.Fingers 62 are pierced out of the surface of lever arm 44 and thus canbe made in the same operation as aperture 46 and opening 48 when leverarm 44 is blanked progressively through the die from strip steel. Whenassembled, the three spacer rivets 22, 24 and 26, in addition to anchorpin 36, are inserted through apertures 30, 32, 34 and 40 respectively,and are firmly staked in one operation. In this fashion, an integralstructure is formed with the plates spaced apart approximately 0.200 to0.220 inches.

Upon assembly, support plates 18 and 20 are axially and radially alignedand securely welded to spindle 50 or axle tube 118 by welds 68 (FIG. 3)through mating semicircular mounting notches 70 centrally formed inlower portion 72 of plates 18 and 20.

Brake assembly 10 has two conventional brake shoes 58 and 60, each ofwhich includes accurately-shaped table 74 and outer brake lining 76, anda centrally supported inner, generally upright, web 78.

Anchor pin end 80 of each of the webs 78 is provided with a semicircularnotch 82 adapted to engage the central diameter portion 84 of anchor pin36. A right angle notch 85 is vertically disposed below notch 82, beingdimensioned to mate with actuating lug 56 of lever arm 44, previouslydescribed. Rectangular notch 86, centrally formed in lower end 88 ofeach web 78 is adapted to interengage with similarly dimensioned slot 90formed in the ends 92 of conventional brake adjustment assembly 94.

When assembled, brake shoes 58 and 60 are substantially supported in aprecise axial alignment by webs 78, being adapted to closely fit betweenbacking plates 18 and 20 in regions "A", "B", "C", and "D" as shown inFIG. 2. Semicircular notches 82 in ends 80 of webs 78 are maintained inspring biased engagement on opposite sides of anchor pin 36 by a pair oflike tension springs 96. Each of springs 96 is provided with hooked ends98 which are engaged in notched holes 100 in webs 78 of brake shoes 58and 60.

Brake shoes 58 and 60 coact at lower ends 88 through conventional brakeadjustment assembly 94, being maintained in connecting engagement bytension spring 102 provided with hooked ends 104 whereby it is coupledbetween opposing holes 106 notched in webs 78. The rotating elements ofbrake assembly 10 consist of drum 108, drum back 110, armature plate 67and hub 114. Drum 108 is supported for rotation about brake shoes 58 and60 by drum back 110 which is conventionally attached or formed togetherwith rotating hub 114. Armature 67 is a ferous, disc-shaped member andis either formed integral with a hub or is a separate disc which istypically attached by rivets 116 to drum back 110. It has a flat faceoriented perpendicular to the axis of drum 108 and is axially positionedto normally rotate in low friction contact with electromagnet 66. Hub114 is rotably supported in a conventional fashion on stub axle 50 byroller bearings and a securing means, not shown. Stub axle 50 in turn,is typically welded to the main axle 118 of the vehicle and extendsbetween stub axles 50 on either side of the vehicle, being normallyattached in a conventional fashion through suspension mounting pads 121.

Of particular significance is the fact that the invention enables themounting of the brake assembly further outboard than possible with knowndesign, that is, nearer the bearing journal on which hub and drumassembly 12, and wheel and tire assembly 14, are mounted. In fact, thisdistance has been reduced by more than one inch over current designs toenable this distance to be typically reduced from 3 11/16 to 21/4inches. A range of 2 to 21/2 inches for this dimension may be achievedwith the design of the invention. The significance of this isillustrated in FIG. 3 wherein the downward force of the vehicle load onsuspension pad 121 is supported by the opposite or upward force appliedto spindle 50 by wheel and tire assembly 14 supported by ground 122. Theresult is that there is significantly less flexure of the axle assemblybetween the points of mounting of the brake assembly and the drumassembly and this assures much better alignment between the brake shoesand the brake drum and thus greater wear.

OPERATION OF ELECTRICAL BRAKE

Assume, initially, that drum 108, and the wheel 14 to which it isconnected on a vehicle, is rotating in a counterclockwise directionrepresenting forward motion of the vehicle. In order to apply brakingforce, power is applied to input leads 120 of electromagnet 66 through aswitch normally located in the cab of a tractor towing the vehicleincluding brake assembly 10. A magnetic flux is then produced byelectromagnet 66 which causes it to be attracted into a high frictioncontact with armature plate 67 and this in turn causes lever arm 44 tobe rotated about rivet 24 a few degrees in a counterclockwise direction.

In this manner, actuating lug 56 of lever arm 44 is turned to apply aforce upon engaging surface 85 at the top end of web 78 of (primary)shoe 58, causing shoe 58 to be moved radially outward into frictionalengagement with inside diameter of drum 108. This in turn causes thebottom end 88 of web 78 of shoe 58, to apply a radial pushing forcethrough brake adjustment assembly 94 to secondary shoe 60 and thus bothbrake shoes coact to apply a substantial braking outward radial force tobrake drum 108 and thus to wheel 14 of the vehicle attached thereto. Theresult is, of course, that a braking force is transmitted through anchorpin 36, to backing plates 18 and 20 to axles 50 and 118 and then to thesupported vehicle causing it to be brought to a halt. Thus this brakingforce is transmitted from brake shoes 58 and 60 to the axle 50 along aplane perpendicular to the axle 50 and which is normal to the surface ofthe shoes 58 and 60 and which also intersects the center line of same.

Assume next that a braking action is to be applied to a vehicle movingin the opposite direction wherein brake drum is initially turning in aclockwise direction. Lever arm 44 would then be pivoted in a clockwisedirection by armature disc 67 to initially cause lug 56 to engage uppersurface 85 of shoe 60 and cause shoe 60 to move into engagement withbrake drum 108. This action in turn causes the lower end of brake shoe60 to apply force to drum 108 which is transmitted to shoe 60 whichcoacts with shoe 58 to apply an increased braking effect, in like manneras described above, to again bring the vehicle to a halt.

An alternate electromagnetic assembly is shown in FIGS. 1A and 1Bwherein a circular electromagnet 130 is provided with a rectilinearmounting slot 132 centrally formed in center pole piece 133 of magnet130. Oppositely positioned retaining lugs 136 are formed in upper andlower lateral walls of slot 132 at a point midway between vertical walls138 and 140 which extend inward from rear surface 142 of magnet 130.Retaining lugs 136 are of a width dimension so as to freely engage theinner edges of spaced mounting fingers 62 previously described. Whenassembled to fingers 62, magnet 130 is secured to fingers 62 by springclip 143 typically formed of flat strap material. Spring clip 143includes U-shaped member 144 which is adapted to frictionally engageover the lower end of brake actuating arm 44. Forward arm 146 of Umember 144 is formed so as to mate with the lower surfaces of mountingfingers 62 and is provided with an elongated rectangular slot 148. Onceassembled over brake actuating lever 44 as shown in FIG. 1B,electromagnet 130 is forcibly engaged over forward connecting member 150of rectangular slot 148 and lower retainer lug 136 is slidably retainedby slot 148 while an upper lug 136 is adapted to guide magnet 130 beingengaged with the inner surfaces of fingers 62. Electromagnet 130 is heldin loosely sliding contact with armature plate 67, FIG. 1, by tensionspring 152 supported at one end by rear surface 142 of magnet 130 and atthe opposite end by the forward surface of actuating lever 44.

As an added feature splash plate 154, shown in FIG. 1C, protects movableparts of brakes herein described from dirt, water, and other grittymaterial which is encountered by a vehicle to which they are attached.Splash plate 154 is typically formed of high-impact plastic and includesa central supporting section 156 having integrally formed ribs 158 andis provided with a central opening 160 adapted to mount to vehicle axle118. An outer ring 162 formed in the shape of a circular trough isadapted to freely receive the inner edge of brake drum 108 (FIG. 1).Splash plate 154 is attached about vehicle axle 118 through radial slot164 formed between the outer perimeter of splash plate 154 and centralopening 160. It is supported to brake assembly 16 by a bracket (notshown) attached to backing plate 18 which is adapted to accept an innertrough-shaped mount 166 being firmly secured thereto by pins or bolts168, or alternately, plate 154 may be clamped.

FIGS. 4-8 illustrate four alternate methods of activating the brakes byhydraulic means instead of by electromechanical means. In FIG. 4 twinplates 170 and 172 are appropriately spaced by spacer rivets 174 and 176and anchor pin 178, as better illustrated in FIG. 3. Elongated cutouts180 are formed in each of plates 170 and 172 which are adapted toreceive a dual hydraulic cylinder 182. Cylinder 182 is supported bythree mounting lugs 184, two of which are secured rearward of plate 170by bolts 186 and the third upper lug 184 which is secured to rear plate172 by bolt 186. In order to facilitate removal of hydraulic cylinder182 a cutout 188 is made in forward plate 170 through which lug 184 isinserted, while rearward plate 172 is provided with similar cutoutsthrough which lugs 184 are removably attached to forward plate 170. Whenassembled, brake shoes 190 and 192 are substantially supported in aprecise axial alignment by webs 194, being adapted to closely fitbetween backing plates 170 and 172 in regions A, B, C and D.Semicircular notches 196 in the upper ends of webs 194 are maintained inspring biased engagement on opposite sides of anchor pin 178 by a pairof like tension springs 198. Each of springs 198 is provided with hookedends 200 which are engaged in notched holes 202 formed in webs 194 ofbrake shoes 190 and 192. Elongated notches 204 are formed inward of theupper end of webs 194 which are provided with an inward facing endsurface 206 adapted to engage shoe contacting pins 208 of dual wheelcylinder 182. Brake shoes 190 and 192 are innerconnected at their lowerends by brake adjustment assembly 210 and tension spring 212 which isprovided with hooked ends whereby it is coupled between holes 214notched in webs 194. The hydraulic brake assembly of FIG. 4 is typicallysupported to a spindle as by welds in a manner illustrated with respectto FIG. 3.

In order to apply a braking force, hydraulic pressure is applied towheel cylinder 182 as by foot pedal operation of the master brakecylinder. This causes the pistons and thus shoe contacting pins 208 tomove outward applying opposing forces to operating surfaces 206 of shoes190 and 192. As a result shoe braking surfaces 216 and 218 are pressedagainst a brake drum in the same manner and with the same effect asdescribed with respect to the electrical brake of FIG. 1. Thus thisbraking force is transmitted from brake shoes 190 and 192 to a spindlealong a plane perpendicular to the spindle and which is normal to thesurface of shoes 190 and 192 and which also intersects the center lineof shoes 190 and 192 as previously described.

FIG. 5 is a cross sectional view taken along the lines 5--5 of FIG. 4and is illustrative of a dual acting pneumaticmechanical brake assembly220 which when mounted in place of hydraulic cylinder 182 of FIG. 4 hasthe same outward appearance. Circular guides 222 are slidably retainedwithin the outer end regions of cylinder 224, being provided on theinwardly facing ends 226 with a transverse slot 228 which is dimensionedto accept roller bearings 230. Wedge shaped actuating arm 232 issupported by the inwardly facing surfaces of roller bearings 230.Outwardly disposed ends 234 of circular guides 222 are provided with aconically shaped socket 236 which is adapted to freely receive a likedimensioned end of shoe contacting pins 238. The opposite ends ofcontacting pins 238 extend outward through openings 240 formed inpliable seals 242 which close the opposite ends of cylinder 224 toprevent contamination from collecting on the sliding surfaces ofcylinder 224 and sliding guides 222. Brake contacting pins 238 areconfigured on the ends so as to accept slots, not shown, provided in endregions 206 of webs 194, as shown in FIG. 4. Actuating arm 232 extendsoutward through cylindrical access compartment 244, covered by suitableflexible dust cap 246 and thence through a protective dust cap 248 inthe outer wall of pneumatic assembly 250. The inner end 252 of actuatingpin 232 is centrally secured to flexible diaphragm 254. Diaphragm 254 issuitably supported within ovular housing 256 which is in turn supportedby bracket 258 to a suitable non-rotating member such as a vehicle axle,not shown. Brake shoe 190 and 192 are held in firm engagement withanchor pin 178 (FIG. 4) by a pair of like tension springs 198, bettershown in FIG. 4.

Pneumatic-mechanical actuating assembly 220 operates as follows. Assumeinitially that a vehicle to which backing plates 170 and 172 areattached is in motion and that the drum which surrounds brake shoes 190and 192 is rotating. To apply a braking force, air pressure isselectively applied through inlet line 260 (or vacuum applied tocompartment 263) from a valve, not shown, connected, for example, to abrake pedal, which pressurizes the rear compartment 262 of pneumaticassembly 250. Diaphragm 254 is moved toward the left which pushesactuating arm 232 into further engagement with roller bearings 230.Inclined surfaces of operating arm 232 cause bearings to be furtherseparated and thus move slides 222 outward which action applies anexpanding force through pins 238 to brake shoes 190 and 192 and thus abraking force, as previously described.

The dual acting wheel cylinder with respect to FIG. 4 also readily lendsitself to the hydraulic mechanical assembly shown in FIG. 6. Backingplates 264 and 266 shown in FIG. 6 are also spaced to support brakeshoes 190 and 192, in a manner previously described, by anchor pin 178and strategically placed spacer rivets 174 an 176, as shown in FIG. 3.The assembly is also affixed to a spindle as by welding as describedabove with respect to FIG. 3. Each of plates 264 and 266 in theconfiguration shown in FIG. 6 is provided with a downward extendingregion 268 which has cutouts 180 adapted to receive hydraulic cylinder182 as previously described. In this configuration a pair of similarlevers 270 are pivotally attached at the upper end by suitable pivotpins 272 which are supported by backing plates 264 and 266. Each oflevers 270 includes an upper vertically disposed portion 274 which joinsa central interconnecting region 276, being formed outward so as toprovide free clearance for an axle and which joins, at the lower end 278a vertically disposed pin engaging portion 280. Notches, not shown, arecut into the inwardly facing edges 284 of levers 270 which are adaptedto accept piston connecting pins 286 of hydraulic cylinder 182. Similarnotches, cut in the outwardly facing edges of levers 270 at a point 288intermediate the ends are adapted to interconnect with pins 290 whichextend between levers 270 and operating end surfaces 206 of shoes 190and 192. When assembled, and as described before, anchor pin ends 292 ofwebs 194 are held in firm contact with anchor pin 178 by brakeretracting spring 294. The lower ends of shoes 190 and 192 areinterconnected as before by brake adjusting assembly 210 and spring 212.When thus assembled, brake shoes 190 and 192 are supported withinregions A, B, C, and D between backing plates 264 and 266, as previouslydescribed.

Hydraulic pressure is applied to wheel cylinder 182 in a mannerdescribed above resulting in an outward movement on contacting pins 286.Right lever 270 pivots in a counterclockwise direction which applies anoutward force to surface 206 of right brake shoe 192. Contacting pin 286of cylinder 182 applies a clockwise movement through left lever 270 andconnecting pin 290 to operating surface 206 of brake shoe 190.Accordingly, each shoe 190 and 192 is moved into contacting engagementwith a brake drum, not shown, to apply a braking force as describedabove. It is readily seen that much less hydraulic pressure is requiredto apply an equal force to brake shoes 190 and 192 in view of themechanical amplification ratio provided through levers 270. This form ofthe brake is particularly enabled by virtue of the precise alignment ofthe brake shoes provided by the invention resulting in less necessarytravel of the pistons of cylinder 182. This in turn enables cylinder 182to be sufficiently compact to fit in the limited space in which it mustbe mounted.

FIG. 7 shows how a dual cylinder hydraulic brake assembly 296 issupported by spaced backing plates 298 and 300. In this configuration,backing plates 298 and 300 are cut into a hexagonal shape whereupon theyare then held in spaced relationship by spacer rivets 174 and 176 andanchor pins 178 (better shown in FIG. 3). Each of plates 298 and 300have oppositely positioned cutouts 306 which are dimensioned to accept asingle hydraulic cylinder 308 which is removably attached by suitablelugs 310 to rear backing plate 300 and forward backing plate 298. Whenassembled, webs 312 of brake shoes 314 and 316 are supported betweenbacking plates 298 and 300 in regions A, B, C, and D, as beforedescribed. One end 318 of each of webs 312 rests against adjusting cam320 which is adapted to maintain brake shoes 314 and 316 in closeproximity to a drum, not shown. The opposite end 322 of each of shoes314 and 316 is supported by anchor pin 178 as shown in FIG. 1 whichextends through a hole, not shown, provided in end region 322 of webs312. Shoe contacting pins 326 of each of wheel cylinders 308 has anouter end configured to accept a slot provided in free end region 328 ofeach of webs 312. Each of shoes 314 and 316 is held in a retractedposition by a pair of like tension springs 330 located on each side ofbacking plates 298 and 300 and which are supported by holes 332 in webs312 and holes 334 provided in backing plates 298 and 300. In operation,equal hydraulic pressure from a master cylinder such as that previouslydescribed, being operated by a foot pedal, is applied outward force toends 328 of brake shoes 314 and 316, forcing them outward radially intocontact with a drum. Assuming that a brake drum, not shown, is rotatingin a counterclockwise direction about shoes 314 and 316 as viewed inFIG. 7, a substantial braking force would be applied to the innersurface of the drum.

An alternate hydraulic brake assembly is shown in FIG. 8 in whichtraingular shaped backing plates 336 and 338 are spaced by spacer rivets174 and 176 and anchor pin 178, as previously described, and each havecutout 306 which is adapted to mount a single wheel cylinder 308. Wheelcylinder 308 is supported by mounting lugs 310 to rear backing plate 338and forward backing plate 336, respectively, by bolts 340. Whenassembled, as shown in FIG. 8, brake shoes 342 and 344 are supported inprecise axial alignment by webs 346 which are adapted to closely fitbetween backing plates 336 and 338 in regions A, B, C and D aspreviously described. The lower ends of brake shoes 342 and 344 areinterconnected by conventional brake adjust assembly 210 and spring 212.The upper end of brake shoe 344 is pivotally supported by anchor pin178, configured as shown in FIG. 1. The upper end of brake shoe 342 hasvertically disposed end surface 347 which is held in contactingengagement with adjustment cam 348 by brake shoe retracting spring 349.Brake shoe contacting pin 326 of wheel cylinder 308 is in contactingengagement with a slot, not shown, provided in end region 347. Onceassembled, the brake is attached to a spindle by welds as shown in FIG.3. Accordingly, brake shoes 342 and 344 are supported in exact axialalignment. In operation, hydraulic fluid under pressure is fed from amaster cylinder, not shown, to wheel cylinder 308 which forcescontacting pin 326 outward. This moves brake shoe 342 into contactingengagement with a drum. Brake shoe 342 then acts through adjustmentassembly 210 to force the lower end of brake shoe 344 into contactingengagement with inner surface of the brake drum and a braking forceapplied as previously described.

FIG. 9 is a top view in perspective of a portion of the brake shown inFIG. 4. It illustrates how a parking or emergency brake lever isattached to a vehicle equipped with brake assemblies which employbacking plates 170 and 172. Anchor pin 350 includes a lever supportshaft 352 which extends beyond shoulder portion 354 by which anchor pin350 is secured to backing plate 170. S-shaped brake actuating cam 356includes centrally formed slot 358 which is adapted to freely slide overshaft 352 and has inwardly formed tines or prongs 360 which aredimensioned to freely accept slots 362 formed above and below hole 364formed in backing plate 170. Once assembled, the inner end regions 366of prongs 360 are adapted to engage end surfaces 368 of webs 194. Leverarm 370 is pivotally attached over shaft 352 through hole 372 centrallyformed in upper circular regions 374 of arm 370. Lower portion 376 ofactuating lever arm 370 is formed in an arc so as to clear a vehicleaxle and is joined to upper curved region 374 by U-shaped member 378which is adapted to clear wheel cylinder 182. Oppositely positionedtines or prongs 380 are integrally formed about upper end region 374 oflever arm 370 and are adapted to engage mating surfaces 382 of brakeshoe actuating cam 356. Lever arm 370 is in turn rotably supported toshaft portion 352 by locking ring 384. Lever arm 370 is actuated bycable 386 attached at its lower end 388. When cable 386 is thustensioned, brake actuating lever 370 is rotated in a counterclockwisedirection and cam 356 rotated counterclockwise, applying an outwardforce through prongs 360 of cam 356 to upper end 368 of brake shoes 190and 192. Brake shoes 190 and 192 are then expanded outward intoengagement with a brake drum to apply a substantial parking brake forceto the drum.

Referring to FIGS. 10 and 11, there is shown one embodiment of theinvention in which brake shoes 390 and 392 are mechanically expanded oroperated and in which backing plates 394 and 396 are detachablysupported by axle member 398, also removably attached to conventionalmounting flange of vehicle axle 400. Mounting flange 402 is essentiallycircular in form, having an upwardly disposed triangular section 404which is adapted to mount tubular bearing 406, having a centrally formedlongitudinal bearing surface 408. Bearing 406 extends forward ofmounting flange 402 and is provided with an outward shoulder region 410,which is adapted to accept a similarly dimensioned hole 412 formed inupper edge region 414 of backing plate 396. Bearing 406 has an elongatedrear portion 416 which provides a substantial bearing surface foractuating shaft 418. Backing plate 396, when assembled, is held inspaced relationship with respect to forward surface 420 of mountingflange 402 by forwardly projecting standoffs 422, spaced about centralopening 424 in order to appropriately position backing plates 394 and396 with respect to mounting flange 402. Backing plate 396 is attachedto mounting flange 402 through mounting holes 426 which are dimensionedto mate with holes 428 centrally formed in standoffs 422, which in turnmate with holes 430 provided in flange 432 attached to axle 400. Forwardbacking plate 394 is provided with similarly dimensioned holes 434 andis attached in spaced relationship to backing plate 396 by spacers 436,the entire assembly being attached by bolts 438 (FIG. 11) through holes430 to mounting flange 432. Brake-operating cam 440 has a circular innerbody 442 through which is formed an oval slot 444 adapted to accept asimilarly configured end region 446 of brake actuating shaft 418.Diametrically positioned risers 448 of cam 440 have shoe-engagingsurfaces 450, rounded as shown in FIG. 10, to provide low frictionalengagement between surfaces 450 and end surfaces 452 of webs 454 ofbrake shoes 390 and 392. When assembled to actuating shafts 418 (FIG.11), actuating cam 440 is axially supported between the forward surfaceof bearing 406 and forward plate 394. Brake shoes 390 an 392 areconnected at lower ends 456 of webs 454 by conventional brake adjustassembly 458, having a slot 460 at each end, which is adapted to acceptsimilarly dimensioned notches 462 cut in ends 456 of webs 454, and byspring 464, having hooked ends, which are engaged in holes 466 formed inwebs 454. Circular notches 468 are formed in end regions 452 of webs 454which are dimensioned to closely engage central circular portion 442 ofbrake actuating cam 440. When in an unoperated or retracted position,notches 468 of webs 454 are held in spring-biased engagement withoperating cam 440 by like tension springs 470. Springs 470 arepositioned on opposite sides of backing plates 394 and 396, and havehooked ends supported within holes 472 formed in webs 454. A brakingforce is applied to brake shoes 390 and 392 through actuating shaft 418by elongated lever arm 474, having a circular upper end through which isformed an oval notch 476 dimensioned to accept a similarly dimensionedend region 478 of actuating shaft 418. When assembled, as shown in FIG.11, actuating shaft 418 is axially supported by locking rings 480secured within slots 482 formed inward of the ends of actuating shaft418. Lever arm 474 is formed in an arc so as to clear an axle of avehicle and is actuated by brake cable 484 attached to lower end 486 ofarm 474, being typically routed underneath the axle.

It is readily seen that brake shoes 390 and 392 are substantiallysupported by backing plates 394 and 396 and are thus maintained in aprecise axial alignment about axle 400. In operation, cable 484 istensioned by a brake lever located in a vehicle. This applies aclockwise force to lever arm 474. Rounded surfaces 450 of actuating cam440 are thus brought into contacting engagement with ends 452 of webs454. This forces the outer surface 488 of shoes 390 and 392 into contactwith a cooperating brake drum, not shown. Because of the large operatingcam 440 and contoured leading edges 450 of cam 440, an improved,dependable, and even braking force is applied to shoes 390 and 392. Thebrake assembly just described is particularly useful as a service brakeor emergency brake in addition to serving as a desirable parking brake.

Referring to FIG. 12, there is shown a modified version of themechanical brake assembly shown in FIG. 10 wherein one backing plate asa discrete element has been eliminated. Instead of one of the plates,mounting bracket 490 has elongated embossed or raised plate regions 492and 494 formed at opposite sides 496 and 498 of bracket 490. Atriangular-shaped embossment or raised plate region 500 is formed alongvertically disposed end region 502 of bracket 490, all regions being ofequal thickness dimension with respect to the forward surface of bracket490. Four tubular standoffs 504 are spaced about inner circular cutout506 having inner dimensions identical to and in alignment with holes 508formed in backing plate 510. Standoffs 504 are of a greater thicknessthan the plate regions and are adapted to support backing plate 510 whenassembled thereto so as to provide spaced regions between surfaces 512of embossments 492 and 494 and 500 and surface 514 of backing plate 510.There is thus provided spaced plate surfaces which form a guide tosupport webs 454 of brake shoes 390 and 392 in a precise alignment.Brake actuating cam 440, which is formed identical to that describedabove, is provided with a centrally formed oval slot 444 which isdimensioned to receive a like dimensioned end 526 of cam actuating shaft528. Cam actuating shaft 528 is supported by a bearing 530 formedthrough embossment 500 and tubular elongated support 532 which extendsbeyond the rear surface of mounting bracket 490. Actuating lever 474,similar to the one described immediately above, has an oval slot 476formed in an upper circular region adapted to accept like dimensionedend region 544 formed on actuating shaft 528. Once assembled, actuatingshaft 528 is inserted through bearing 530, actuating cam 440, and upperopening 540 of backing plate 510. Actuating lever 474 is assembled tothe opposite end of actuating shaft 528, and the shaft is axiallyretained by locking rings 542 which are dimensioned to fit withincircular slot 544 formed near each end of actuating shaft 528. Brakeactuating lever 474 is curved so as to provide clearance between lever474 and a vehicle axle and has brake cable 484 attached near lower end486. Brake shoes 390 and 392, when mounted, are interconnected at thelower end 456 by conventional brake adjustment assembly 458 and bytension spring 464 having hooked ends adapted to engage holes 466provided in webs 454 of shoes 390 and 392. The upper anchor pin ends 452of webs 454 are held in the same biased engagement with actuating cam440 by a pair of like tension springs 470, supported at the ends byholes 472 formed in webs 454, being disposed outside of backing plate510 and bracket 490. Operation of this brake assembly is identical tothat described immediately above, shown in FIGS. 10 and 11.

FIG. 13 is a fragmented view of a portion of a hydraulic brake assemblyshown in FIG. 4 as viewed from the top. FIG. 13 shows how a parking orservice brake is selectively added to the hydraulic brake.

Brake actuating cam 440, similar to that described above with respect toFIGS. 10-12, is supported by a combination brake actuating shaft andanchor pin 544 which is supported on each end by aligned holes 546formed near the upper end of backing plates 170 and 172. A square socket548 is formed into the end of actuating shaft 544 which is adapted toaccept a similarly dimensioned insert 550 formed on the connecting endregion of lever mounting shaft 552. Shaft 552 is attached to an upperend region of parking brake actuating lever 554. Lever 554 is operatedby brake cable 556 which is attached through pin 558 at the lower end ofbrake lever 554. Lever 554 is appropriately curved, as shown, to clearwheel cylinder 182 and an axle of a vehicle. When brake cable 556 istensioned as by a conveniently located lever within a vehicle, lever 554is moved in a counterclockwise direction and risers 448 of operating cam440 force inwardly disposed ends 560 of webs 194 outward, applying abraking force through surfaces 216 of brake shoes 190 and 192 to a brakedrum.

SUMMARY OF FEATURES

It will be readily seen from the drawings and the foregoing descriptionthat the braking system disclosed herein meets the objectives set forthfor it. Backing plates and lever arms can be simply formed by stampingthem out of strip coil metal plate. While not shown, guide holes may beprovided in the backing plates to facilitate location during welding onaxle or spindle. Further, where additional stiffening or flatness isdesired, ribs may be formed outwardly into the back of each backingplate.

The remaining components, other than backing plates and lever arm, ingeneral, are readily available at relatively low cost. The total numberof components is a reduction over that required for many brakeassemblies of other designs.

As a particular structural feature, FIG. 1, lever arm 44 is supported ina balanced fashion by rivet 24 between plates 18 and 20. By being thusmounted upon a pivoting support which has dual supports or in doubleshear and therefore there is provided substantially greater support thantypically found, wherein the lever pivot is singly supported at one endand in single shear and subject to lever action. This means that notonly is there much less chance that the lever pivot will break but muchless chance, in fact slight if any, that it or the support area willdeform and thus produce a malfunction of the lever arm operating thebrake shoes because of the balanced center line of loads and actions.The same added support is provided anchor pin 36 wherein it and its dualsupporting structure, plates 18 and 20, provide a more rugged anddurable and easily assembled structure.

Since plates 18 and 20 provide a guide during planer operation of leverarm 44, it is assured that lug 56 on lever arm 44 will provide a desireddirection of force on shoes 58 and 60 which is normal to bands 74 andlinings 76 of brake shoes 58 and 60.

The backing plates or guide plates of all embodiments provide a guide inwhich the webs of brake shoes operate and thus there is prevented thetendency of the brake shoes to apply an uneven engaging surface to theworking surface of a brake drum and the shoes maintained as aligned andin position when not engaged. Therefore adjustment of lining clearanceto a drum inside diameter can be minimized and travel to full engagementlessened. Thereby improvement of field life is offered without repeatedadjustments. Maintaining shoe alignment heretofore has been asubstantial problem, wherein the brake shoes are both supported from asingle side of a single plate, which plate deflects with each brakeapplication and is not infrequently distored because of heat and forcesfrom the brakes being transmitted to the plate. In some instances, smalldistortions and stresses arise from the manufacturing process which arethen amplified by heat generated by usage. In the case of the presentinvention, employing dual plates, and wherein the brake shoes areoriented in a balanced fashion, on a given centerline of forces andreactions such heating does not tend to produce distortions which havesuch an effect. For one thing, with the dual plates, there is greaterventilation offered and the conductivity of the heat away from thebrakes to the axle and for another, the cross-support provided betweenthem provide substantial resistance to deformation of the plates.

As still another advantage of the present invention, it enables theshoes to be aligned in use in the same manner in which they are alignedin the final stage of manufacture, that is during the grinding of thelining to the prescribed tolerances. Thus, in this grinding procedure,the webs of the shoes are normally used as a reference plane, the websbeing gripped by the grinding fixture. Similarly in the present brakeassembly, the webs are used as the alignment reference since the websfit between backing plates in an aligned position. In contrast, priorbraking systems have not used the webs as reference alignment means,instead they have used edges of the table of the brake shoe assemblies.The result has been that not infrequently, misaligned brake assembliesare produced, requiring additional grinding of the linings in order thatthe brake shoes will fit inside of the brake drums with which they ae tobe used.

Further improvement set forth herein is in the inclusion of a balancedsystem for return of the brake shoes to a non-engaged posture after theyhave been operated. This is provided by the dual set of return springs470, FIG. 10.

The overall result is that the present invention clearly provides a newbraking system with improved performance and accomplishes this generallyat a lower cost of manufacture.

What is claimed is:
 1. The method of construction of a wheel brakeassembly comprising:stamping from a flat sheet material a single pair ofgenerally delta-shaped flat plates and forming a semi-circular openingin one side edge of each plate, said side edge opening being generallyopposite to an apex region of said plate; with said flat plates spacedand parallel and aligned with said openings adjacent, installing asingle anchor pin between plates near one corner region in a positionopposite said openings, and installing between said plates means forselectively applying a force parallel to the side edge containing saidopenings; rigidly fastening the thus formed flat plates in a fullyspaced and parallel relation together, leaving a clearance for webs ofbrake shoes sufficient for movement of the webs but guided movement byand between said plates; installing brake shoes with webs extending intoand between opposite sides of said plates, and the webs of each being inengagement with said anchor pin; installing a pair of springs onopposite sides of said plates and facing each other in a direction whichis generally normal to a line extending between said anchor pin and thecenter of said semi-circular opening; installing operating meansreactively mounted on said plates for applying a force to the webs ofsaid brake shoes; and positioning said openings in said plates over anaxle member having a like curvature to that of said openings and weldingboth said plates to said axle member.
 2. The method of construction of abrake assembly as set forth in claim 1 wherein there is installed a saidmeans for applying a force parallel to the side edges containing saidopenings, comprising a lever rotably attached to and between said platesand between said webs, and including an electromagnet extending from oneend of said lever, and an opposite end of said lever being adapted toapply a force to an end region of webs of brake shoes positioned betweensaid plates.